Bearings come in a variety of configurations. For example, bearings typically have an inner race, an outer race, and rollers disposed between the inner race and outer race. The rollers may, for example, be ball bearings, cylindrical rollers, or tapered rollers. The rollers may be separated by a cage to maintain constant spacing between the rollers. To increase the life of the bearing, the bearing may be lubricated with a fluid, such as oil or grease. Bearings may be open (i.e., unsealed) or may be sealed. An open bearing may need to be supplied with additional lubrication over time, whereas a sealed bearing may be provided with lubrication that will last for the life of the bearing in the absence of leakage of the lubrication.
Sealed bearings may have an internal or external seal to prevent debris from entering the bearing and to prevent lubricating fluid from leaking out of the bearing. Debris, such as dirt, crop residue, and/or moisture, in the bearings can cause loss of lubrication, corrosion to the rollers and/or the races, and additional wear through abrasion. Loss of lubrication can similarly result in increased wear, such as through increased friction between the rollers and the inner and outer races. Internal bearing seals may be crimped or pressed onto the outer and/or inner races of the bearing to create a single seal or shield extending radially between the inner and outer races. An external seal, such as a lip or ring seal made of elastomeric material, such as rubber, may protect a particular area of the bearing by creating a seal pressing against a portion of the bearing. If these seals are insufficient to prevent containments from entering the bearing or leakage of lubricating fluid, additional seals to ensure adequate sealing, or to provide backup sealing, may be problematic, in that more axial space is taken up by the bearing and seal compared to the bearing alone or the bearing with a simple seal.